Boat
size recommendations are for boats of average windage and proportions in
30 knots of wind, average bottom conditions, and moderate protection from
open seas. Remember that the loads in 42 knots of wind are twice as much
as in 30 knots.

Use
three-strand nylon line, 6-12 ft (2-4 m) of chain and a minimum of 5:1
scope. A minimum of 6 ft (2 m) of chain should be used for every 25 ft (8
m) of water that you usually anchor in. For storm conditions use an anchor
one or two sizes larger.